Numerous machine tools and methods for machining workpieces in a working area are known from the prior art.
In addition to ever increasing accuracy requirements imposed on the machining result, such machine tools and methods are subject to the further requirement that the throughput of workpieces is to be continually increased by such machine tools with little outlay in terms of design and with a high machining accuracy.
A machine tool of the type mentioned at the outset has been disclosed, for example, in DE 101 63 445 A1, which describes a transfer line having a plurality of machining stations and a first transport device by which the workpieces are transported between the machining stations. Second transport devices are provided in the machining stations, the workpiece being transferred from the first to the second transport device by means of a gripper arranged on the first transport device.
The workpiece mounted on the second transport device is then machined in the respective machining station, the workpiece being moved by the second transport device during the machining in order to position it for different machining operations. In each machining station, the workpiece can be machined on opposite sides in each case by a plurality of work spindles.
Furthermore, a robot is provided which loads workpieces to be machined onto the first transport unit and removes machined workpieces from the first transport unit.
In this transfer line, the throughput of workpieces is not sufficiently high, since the workpiece change itself is effected relatively slowly, for the first transport device serves the individual machining stations in succession.
In a machine tool known from DE 103 34 285 A1, two machining units are each provided with a plurality of work spindles, the machining units accessing the workpiece from opposite sides. The work spindles in such a machining unit are spaced apart from each other at a distance which corresponds to the distance between workpieces which are held in one or more clamping devices. The clamping devices are designed to be traversable and pivotable.
In this way, identical machining operations can be carried out simultaneously on all the workpieces in one machining step, it also being possible for the two machining units, by means of their respective work spindles, to machine the workpieces at the same time on opposite sides.
Tool magazines can be provided for both machining units in order to be able to carry out different machining operations one after the other on the same side of a workpiece using one and the same machining unit.
In this machine tool, too, the throughput of workpieces is not sufficiently high, since the tool change requires correspondingly long non-productive time between the individual machining steps.